A car bomber struck a U.S. convoy waiting at an intersection Tuesday in Baghdad (search), killing seven people — including one American soldier — and wounding more than 90. More than a dozen others died in scattered attacks across the capital.

Also, a U.S. Marine assigned to the 2nd Marine Division (search) was killed Monday by small-arms fire in Ramadi, 70 miles west of Baghdad, the U.S. military said. The deaths brought the number of U.S. service members killed in Iraq this month to at least 32.

Violence raged as Iraqi political leaders showed little sign of compromise less than a week before a deadline for approving a new constitution. Faction leaders conferred for about four hours Tuesday night hoping to overcome their differences and produce a charter by Monday.

Participants said the talks focused on Kurdish demands for a federal state and although some progress was made, there was no final agreement on the issue. More talks were set for Wednesday.

The American convoy was stopped at a busy intersection when a driver detonated a vehicle packed with explosives, the U.S. Army said. Six Iraqi civilians also were killed; scores of Iraqis and two U.S. soldiers were wounded.

At least 1,836 members of the U.S. military have died since the Iraq war started in March 2003, according to an Associated Press count.

The United States hopes progress on the political front, including adoption of a democratic constitution, will help deflate the Sunni Arab-led rebellion and enable the Americans and their partners to begin withdrawing troops next year.

"It's important that they stay with their timetable" on the constitution, Defense Secretary Donald H. Rumsfeld (search) said Tuesday. "This will be a critical step in persuading the majority of the Iraqis that the new Iraq is worth fighting for, that they have a stake in it."

Rumsfeld told Pentagon reporters that the constitution "could well turn out to be one of the most powerful weapons to be deployed against the terrorists" and the insurgents are "determined to stop the constitutional process through terror and intimidation."

Late Tuesday, representatives of political factions met for a second round of talks aimed at breaking the deadlock over the constitution, which the parliament must approve by Aug. 15. Talks were postponed Monday by a severe sandstorm.

The constitution also needs approval from voters in an Oct. 15 referendum. Passage would lead to elections in mid-December.

At the beginning of the meeting, presidential spokesman Kamran Qaradaghi told reporters the latest talks would focus on federalism, distribution of wealth and the elections law.

Kurds demand that Iraq be transformed into a federal state so they can continue to run their autonomous mini-state in the north. Sunni Arabs oppose federalism because they fear the Kurds want to secede and dismember Iraq.

Kurdish leader Massoud Barzani joined the talks Tuesday. Barzani, who was stranded in northern Iraq by the sandstorms, has vowed not to compromise on federalism.

A prominent Sunni Arab on the constitutional committee, Saleh al-Mutlaq, suggested that federalism be decided by the parliament to be elected in December.

"We will not accept federalism in these circumstances," al-Mutlaq told The Associated Press. He warned that if Kurdish demands are accepted, "they will have grave consequences" for the future of Iraq. He did not elaborate.

Kurdish parliament member Mahmoud Othman said that during the meeting, U.S. Ambassador Zalmay Khalilzad repeatedly called President Jalal Talabani and parliament speaker Hajim al-Hassani for updates — a sign of U.S. pressure for a deal.

"The problem is that they started discussing the most difficult issue," Othman said, referring to federalism.

Iraqi Prime Minister Ibrahim al-Jaafari, a Shiite, hinted that political leaders might not resolve all issues before next week's deadline but said he remained hopeful the draft could be completed by then.

"But if some matters block us ... then it might take a little time" after the Monday deadline, he told AP.

Al-Jaafari said Iraqi leaders have struggled against deadlines before — including forming a new government after January elections — and were able to meet them.

Asked if leaders would succeed this time, he said: "We hope so, God willing. I see that most of the groups have a strong will, and, God willing, we will cooperate to finish it."

In other developments:

— U.S. troops Tuesday killed four insurgents trying to plant a roadside bomb in the city of Ramadi, police Lt. Mohammed al-Obeidi said.

— Violence targeting Iraqi police left 10 officers dead, including five policemen slain while sleeping in their car. Lt. Col. Ahmed Aboud said the men had spent the night on patrol and were waiting for replacements.

— Late Tuesday, gunmen killed an Iraqi Cabinet employee, Abbas Ibrahim Mohammed, in Baghdad. In addition, three civilians were killed in a mortar attack, police said.

— U.S. and Iraqi forces killed two insurgents and arrested 22 others in northern Iraq, the U.S. military said Tuesday. Soldiers from the U.S. Army's 3rd Battalion, 21st Infantry Regiment killed the insurgents, found setting up a mortar tube Monday in Mosul.

— The mayor of Baghdad, Alaa al-Timimi, was fired and responsibility for managing the city transferred to the provincial governor, government spokesman Laith Kubba said. He refused to say why the provincial council sacked the mayor.

— The mayor of Samawah, a southern Shiite city gripped by riots over lack of municipal services, resigned under pressure. The decision came Monday during a visit by delegates sent by the prime minister, according to Sheik Mohannad al-Gharrawi.

About 750 Japanese troops are based in Samawah, 230 miles southeast of Baghdad.